1. Field of Invention
This invention relates to flashlights, and in particular to a handheld flashlight that can be telescopically adjusted to hold a variable number of batteries, accommodated by the actuation of one or more lamp bulbs in a single head assembly for improved versatility and reliability.
2. Description of Prior Art
Heretofore, a wide variety of flashlights of various shapes and sizes have been proposed and implemented for use as portable light sources. In particular, it is known that certain of these handheld flashlights utilize two or more dry cell batteries, carried in series alignment inside a cylindrical tube or barrel. Generally, the number of batteries in a given flashlight, regardless of shape or size is fixed, indicating that if one battery fails, the flashlight is rendered useless, unless a replacement battery or another flashlight is readily available. In many emergency situations, other batteries or flashlights are not availble, thus causing serious problems or inconvenience.
Although the technology for manufacturing dry cell batteries have advanced significantly over the years, the basic concept is essentially the same. It is common knowledge for example that, it is still difficult in practice to predict how many ampere hours a dry cell battery will deliver, or precisely how long it will last. Basically, the amount of electricity actually stored in a battery depends primarily on the size of the battery, and the skill and knowledge of the manufacturer. Typically, the amount of electricity which can be obtained from a dry cell battery depends very largely on the rate at which the battery is discharged, that is the amount of current which the battery is called upon to deliver. More often than not, the discharge rate will vary from battery to battery, even when batteries are in use under similar conditions, which means that all batteries in a flashlight will not necessarily discharge at the same rate or time. This can be a serious disadvantage under certain circumstances especially when a flashlight is needed, and just one battery is dead. In some instances, it is exacerbated by flashlight users when batteries of different qualities are used in the same flashlight or when older batteries are mixed with newer ones, but of course in cases of emergency it is advisable to use any flashlight battery that will temporarily solve the problem. From the foregoing information, it can be seen that with flashlights in particular, series circuits are very vunerable to failure if one component in the circuit fails, such as a battery, lamp bulb, or switch, which obviously lessens the efficiency.
Moreover, the possible failure of the flashlight lamp bulb is another very important consideration, which is crucial to flashlight operation. In comparison to battery technology, lamp bulbs have been vastly improved over the years, even to a greater degree. Specifically, the intensity, versatility, and longevity of flashlight lamp bulbs have improved via the development of better filiaments, different eases and envelopes used, along with improved manufacturing procedures. Flashlight bulbs can now be produced to last longer, burn brighter, and operate over a wider range of voltage and current, but even with these advancements, it is still a big disadvantage to rely on a single lamp bulb in a series circuit. This is because the life of flashlight bulbs, in spite of improvements are still unpredictable, just as batteries, and will often burn out at an inconvenient time. Flashlight bulbs can burn out as a result of age, improper use or just a defect in manufacturing.
Another consideration involves the variable dispersion of the flashlight beam, which has been limited by some flashlights that use specialized light bulb designs. Although these lamp bulb designs allow for sharper focus of the light beam, most standard or universal type bulbs as a rule cannot be used with these particular flashlights, which can sometime represent a major problem when such a specialized bulb burn out, and there is no available replacement.
Most users, therefore would find it most desirable to have a more economic and reliable flashlight that use standarized components, wherein the possibility of failure is minimized, along with eliminating the need to have multiple flashlights of different lengths and sizes.